Efficiency of retrieval correlates with "logical" reasoning from causal conditional premises

In two experiments, we examined the prediction that there should be a relation between the speed with which subjects can retrieve potential causes for given effects and their reasoning with causal conditional premises (if cause P, then effect Q). It was also predicted that when subjects are given effects for which there exists a single strongly associated cause, speed of retrieval of a second potential cause should be particularly related to reasoning with invalid logical forms--namely, affirmation of the consequent and denial of the antecedent. In the first experiment, 49 university students were given both retrieval tasks and conditional reasoning problems. The results were generally consistent with the predictions. The second experiment, involving 57 university students, replicated the first, with some methodological variations. The results were also consistent with the predictions. An analysis of the combined results of the two experiments indicated that individual differences in efficiency of retrieval of information from long-term memory did predict performance on the invalid logical forms in the predicted ways. These results strongly support a retrieval model for conditional reasoning with causal premises.